Cell Cycle Regulation PDF

Topic 10: Cell Reproduction: The Cell Cycle Cell Cycle Regulation Dr Constantina Constantinou Professor of Molecular Cancer Biology [email protected] PowerPoint Lectures...

Topic 10: Cell Reproduction: The Cell Cycle Cell Cycle Regulation Dr Constantina Constantinou Professor of Molecular Cancer Biology [email protected] PowerPoint Lectures for Biology, Seventh Edition Monday Neil Campbell and Jane Reece December 2, 2024 Lectures by Chris Romero Copyright©©2005 Copyright 2005Pearson PearsonEducation, Education,Inc. Inc.publishing publishingasasBenjamin BenjaminCummings Cummings  Learning objectives (LOBs) Part B (session 1 and 2): Cell cycle regulation 1. Describe cell cycle control through the checkpoints, including the role of cyclin-cdks, the tumour suppressor genes Rb and p53, and cdk inhibitors (CKIs) in cell cycle regulation. 2. Describe the characteristics of cancer cells related to cell cycle dysregulation, including the difference between benign and malignant tumours. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Recommended Reading Recommended reading: Chapter 12, Campbell Biology. Additional reading: Chapter 17, Alberts, B. et al, Molecular Biology of the Cell (2008) 7th Ed. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Part A Summary: Phases of the Cell Cycle The cell cycle consists of: – Interphase: G1, S and G2 phases – Mitotic phase (M): Mitosis and Cytokinesis INTERPHASE S G1 (DNA synthesis) G2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.5 Why do we need to learn about cell division and understand Cell Cycle regulation?  Normal Cell Division Daughter cell 1 Parent cell Daughter cell 2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Uncontrolled cell division Daughter cell 1 Parent cell Cell division has to be tightly controlled to avoid uncontrolled cell division which leads to carcinogenesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Lack of Homeostasis = Carcinogenesis Internal stimuli External stimuli Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  What is cancer? Cancer is uncontrolled cell growth: an abnormal growth of cells which tend to proliferate in an uncontrolled way and, in some cases, to metastasize (spread) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  What is cancer? Malignancy is the tumour property to invade nearby tissues and spread (metastasise) to other parts of the body Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Different types of cancers and incidence At least 200 forms of cancer (and many subtypes for each) Cancers with highest incidence: 1. Breast 2. Lung 3. Colorectal https://gco.iarc.fr/today/data/factsheets/cancers/39-All-cancers-fact-sheet.pdf Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cancer mortality Almost 10 million deaths in 2020 https://gco.iarc.fr/today/data/factsheets/cancers/39-All-cancers-fact-sheet.pdf Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Carcinogenesis Cancer= environment + genetic predisposition Carcinogens: substances and exposures that can lead to cancer Type Example Chemical Benzene Alkylating agents (chemotherapy) Mutations Environment leading to Physical X-rays UV light uncontrolled Viral Hepatitis B cell Human Papilloma proliferation and inhibition of apoptosis Hereditary cancer Li-Fraumeni syndrome Genetic predisposition syndromes predisposition Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Carcinogenesis= activation of oncogenes and inactivation of tumor suppressor genes Activation of oncogenes+ inactivation of tumor suppressor Cancer genes Mutations Cell containing Normal excessive cell mutations Uncontrolled cell division / Defective pathway of apoptosis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Carcinogenesis is a multi-stage process involving multiple hits Colon EFFECTS OF MUTATIONS 1 Loss of tumor- 2 Activation of 4 Loss of suppressor gene ras oncogene tumor-suppressor Colon wall APC (or other) gene p53 3 Loss of 5 Additional tumor-suppressor mutations gene DCC Normal colon Small benign Larger benign Malignant tumor epithelial cells growth (polyp) growth (adenoma) (carcinoma) Fearon ER and Vogelstein B. Cell, 1990 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In order to understand how cancer develops we need to understand how the Cell Cycle is regulated  Cell cycle control The frequency of cell division varies with cell type – Skin cells divide frequently throughout life – Liver cells maintain ability to divide in response to a certain need – Most nerve cells do not divide in a mature human (exceptions) These cell cycle differences result from regulation at the molecular level The cell cycle is regulated by a molecular control system – Cytoplasmic molecules regulate progress through the cell cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle control There are certain control points in the cell cycle where stop and go ahead signals can regulate the cell cycle The control points are known as Checkpoints – They control the transition from one phase of the cell cycle to the next one – They ensure that certain processes have been completed (e.g. completion of DNA replication, presence of growth factors) before another phase starts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle Checkpoints 3 important Checkpoints: – G1 Checkpoint – G2 Checkpoint – M Checkpoint Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle Checkpoints G1 Checkpoint (also called G1/S checkpoint or Restriction point R): – At the end of G1 phase (e.g. checks for the presence of growth factors) – Controls the transition from the G1 phase to the S phase (DNA replication) G1 checkpoint Control system S G1 M G2 M checkpoint G2 checkpoint Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  Cell cycle Checkpoints G2 Checkpoint: – Controls the transition from the G2 phase to the Μ phase (mitosis) G1 checkpoint Control system S G1 M G2 M checkpoint G2 checkpoint Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  Cell cycle Checkpoints M (Metaphase) Checkpoint: – Controls the transition through the stages of mitosis (e.g. correct chromosome alignment in the mitotic spindle during metaphase) G1 checkpoint Control system S G1 M G2 M checkpoint G2 checkpoint Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  The Cell Cycle Control System Three major checkpoints: G1, G2, M G1 checkpoint Control system S G1 G2 M M checkpoint G2 checkpoint Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  The Cell Cycle Control System (G1, G2 and M Checkpoints) Check extracellular environment? Growth factors present? Check if the cell size is ok (is the cell large G1 checkpoint enough to divide)? Check DNA damage? Control system S G1 G2 M M checkpoint G2 checkpoint Check DNA damage? Are all the chromosomes correctly aligned in the Check completion of DNA mitotic spindle? replication? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  The Cell Cycle Control System (G1, G2 and M Checkpoints) G1: checks for cell size, nutrients, growth factors, DNA damage G2: checks for DNA damage, DNA replication completion M: checks for chromosome alignment at mitotic spindle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Damage detected at Checkpoints 1. If DNA damage is detected at the checkpoints G1 and G2 this will lead to G2 and M cell cycle arrest (also known as cell cycle Checkpoints block) 2. This gives the opportunity to the cell to try to repair this damage 3. If this is not possible, this will lead to apoptosis (programmed cell death) 1. Stop the cycle 2. Attempt DNA repair G1 (G1/S) 3. Induce Apoptosis Checkpoint (Programmed Cell Death) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The G1 Checkpoint G1 is the most important Most cells in the checkpoint for many cells human body are in G0 phase Checks for cell size, nutrients, growth factors, DNA damage After G1 checkpoint the cell commits to the cell cycle in the absence of growth factors G0 (mitogenic stimulation no longer needed) G1 checkpoint G1 G1 (a) If a cell receives a go-ahead signal (b) If a cell does not receive a go-ahead at the G1 checkpoint, the cell signal at the G1 checkpoint, the cell exits the continues on in the cell cycle. cell cycle and goes into G0, a nondividing state. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.15 A, B Which molecules make up the cell cycle control system? Cell Cycle Control: Cyclins and Cyclin-Dependent Kinases (1) Cell cycle control is maintained by protein complexes which are composed of 2 subunits: – Cyclin (cyc): the regulatory subunit – Cyclin depended kinase (cdk): the catalytic subunit Kinases are enzymes that inactivate/activate other proteins by phosphorylation Regulatory subunit Catalytic subunit Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Cycle Control: Cyclins and Cyclin-Dependent Kinases (2) Cdks are present at a constant concentration in the cell and are inactive most of the time and become activated by binding to a particular cyclin The concentration of cyclins fluctuates in the cell The active form of cdks (cyc-cdk) can phosphorylate various proteins and can lead to protein activation or inactivation – e.g. phosphorylation of G1/S transcription factors necessary for DNA replication Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Cycle Control: Cyclins and Cyclin-Dependent Kinases (3) Cyclin-cdk holoenzyme Regulatory subunit (cyc-cdk complex) Catalytic subunit Binding of cdks Phosphorylation to different of different cyclins substrates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Cycle Control: Cyclins and Cyclin-Dependent Kinases (4) The activity of cdks is regulated by degradation of cyclins by the proteasome – Proteasome: giant protein complex that binds to protein molecules (short lived proteins such as cyclins and misfolded proteins) and degrades them (proteolysis) – Proteins destined for degradation by the proteasome are first tagged with ubiquitin (small regulatory protein that is ubiquitously present in cells and plays a crucial role in targeting proteins for degradation) – Addition of ubiquitin to proteins is facilitated by enzymes known as ubiquitin ligases (E3 ligases) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Cycle Control: Cyclins and Cyclin-Dependent Kinases (5) Tight regulation of cdks is very important – Loss of cell cycle control can lead to unregulated cell proliferation => carcinogenesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Different Cyclin-Cdks trigger different steps in the Cell Cycle Binding of cdks Phosphorylation to different of different cyclins substrates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  I. Cell cycle regulation during Mitosis by MPF The signal that sends cells into mitosis was named MPF (Mitosis Promoting Factor (also called Maturation Promoting Factor)). MPF was the first Cdk to be discovered MPF consists of a mitotic cyclin (cyclin A or cyclin B) and cdk-1 MPF induces the progression from G2 to M phase by: – phosphorylation and inactivation of Anaphase promoting complex (APC) which is a E3 ubiquitin ligase (which targets S and M cyclins for degradation) – phosphorylation of proteins of the nuclear lamina→ fragmentation of the nuclear envelope Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  MPF: Mitosis control MPF (Mitosis Promoting Factor) cdk1 Cyclin A or Cyclin B Regulatory Catalytic subunit subunit MPF= cyc-A/cdk-1 or cyc-B/cdk-1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Negative Regulation of MPF activity by APC APC (Anaphase Promoting Complex) is a E3 ubiquitin ligase which inactivates mitotic cyclins (cyc-A/cyc-B) and hence MPF during interphase Proteolysis of mitotic cyclins at the end of mitosis => reduction of ΜPF activity Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The activity of cyclins and cdks during the cell cycle Interphase MPF= cyc-A/cdk-1 or cyc-B/cdk-1 (G1/S/G2): APC active → MPF inactive 5 M phase: MPF active → APC Copyright © 2005 Pearson Education, Inc. publishing inactive as Benjamin Cummings Figure 12.16 B  The activity of cyclins and Cdks fluctuates during the cell cycle Cyclin Time 5 M phase: MPF active → Interphase APC inactive (G1/S/G2): APC active → MPF inactive Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.16 A  ΜPF role: cell cycle regulation in Mitosis Chromosomal condensation Nuclear envelope degradation Mitotic spindle formation Chromosome migration to opposite poles Organelle reformation Cytokinesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  II. Cell cycle regulation during interphase 1 Growth factor (mitogen) signalling 2 Expression of early response genes 3 G1 cyclin-dependent kinase (CDK) activity 4 Transcription of genes encoding proteins required for DNA synthesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle regulation during interphase 1. Mitogens (growth factors) – External signals that stimulate cell division by triggering pathways that lead to cell cycle progression 2. Expression of early response genes: – G1 cyclins and cdks: cyc-D, cyc-E and cdks 2,4,6 – Transcription factors: c-Fos, c-Jun and E2F responsible for transcription of genes required for DNA replication (S phase genes: e.g. DNA polymerase) 3. Activation of G1 cyclin-cdk activity – Cyclin D/CDK4/6 and cyc-E /cdk2 complexes become active in G1 and phosphorylate Rb leading to its inactivation – Inactivation of Rb releases E2F, a transcription factor that drives the transcription of genes essential for DNA synthesis 4. Transcription of genes for DNA synthesis – Activated E2F promotes transcription of DNA synthesis genes, including DNA polymerases and other factors needed for S phase entry Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle regulation during interphase If the mitogen is removed: – → reduction in the cyclin-cdk levels – → the cell does not pass through the restriction point R – → the cell does not replicate Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle control by cyc-cdks G1 cyclins-cdks: Early: cyc-D/cdk-4/6, then cyc-E/cdk-2 S phase cyclins-cdks: cyc-A/cdk-2 (required for DNA replication) Mitotic cyclins-cdks: cyc-A and cyc-B/cdk-1 (MPF) G1 checkpoint Early G1: cyc-D/cdk-4/6 Control and 6-12 hours system S S: cyc-A/cdk-2 Late G1: G1 6-8 hours cyc-E/cdk-2 M G2 1 hour 3-4 hours M checkpoint G2 checkpoint M: cyc-A and cyc-B/cdk-1 (MPF) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  Cell cycle control by cyc-cdks Cell cycle progression and cell division are driven by the sequential activation, and subsequent inactivation, of cyclins and cyclin dependent kinases Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Yang et al., Chapter 8. The cell cycle pp197-219. Which molecules make up the cell cycle control system? Cyclins/ Cdks Any other key players? Tumor Suppressor Genes  The Cell Cycle and Tumour Suppressor Genes The cell cycle is tightly controlled by Tumour Suppressor Genes The protein products of tumour suppressor genes inhibit cell division, thereby preventing the uncontrolled growth that contributes to cancer Two very important tumour suppressor genes are RB1 and TP53 which produce proteins Rb and p53 respectively Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Regulation of the Cell Cycle by tumour suppressors 1 2 3 CDK inhibitor p53 (CKIs) 4 Rb 1 Growth factor (mitogen) signalling p53 and Rb are 2 Expression of early response genes tumour 3 G1 cyclin-dependent kinase (CDK) activity suppressors 4 Transcription of genes encoding proteins required for DNA synthesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cell cycle regulation by Rb Retinoblastoma protein (Rb) – Tumour suppressor gene →codes for tumour suppressor protein→inhibits cell cycle progression – Sequesters the transcription factor E2F → Inhibits E2F activation (during G1) Regulation of Rb – G1 phase: Rb dephosphorylation by PP-1 (protein phosphatase-1) – At the end of G1 phase cyc-cdks Cyclin D/cdk4/6 and cyclin E/cdk2 phosphorylate Rb – Phosphorylated Rb cannot sequester E2F – Ε2F is released (activated) => cell enters the S phase Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Rb protein is a key substrate for G1 cyclin-cdks Inactive Rb P G1: Cyclin D/cdk4/6 Rb Phosphorylated Rb Active Rb Inactive E2F & P cannot bind to E2F Cyclin E/cdk2 P Rb E2F + Unphosphorylated Rb binds E2F Active E2F transcription factor E2F preventing its stimulation of S-phase protein expression Released E2F stimulates expression of S-phase proteins (e.g. DNA polymerase) DNA replication starts (S-phase) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2  Cell cycle control: the role of Rb Phosphorylated Rb Rb dephosphorylation Binding to E2F Mitogens Rb remains phosphorylated during S,G2 and M phase Early G1 phase: Rb active cyc D (unphosphorylated) E2F remains active E2F inactive (bound to cyc E Rb) S,G2,M phase: Rb inactive Towards end of G1 E2F active phase: Phosphorylation of Rb Rb phosphorylation (Rb inactive) E2F release and release of E2F (E2F active) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  What is Retinoblastoma? Retinoblastoma is a malignant tumour of the eye(s) that originates from the retina (light sensitive lining of the eye). This disease is caused by a mutation in the tumour suppressor gene RB1 which encodes for the Rb protein. One (unilateral) or both (bilateral) eyes may be affected and typically it occurs in children less than five years old. Worldwide, about 6000 children develop Retinoblastoma each year. It affects 1:15000 births. There are two forms of the disease: familial (heritable) and sporadic (non-heritable). Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Negative regulators (inhibitors) of the cell cycle Cdk inhibitors (CKIs): inhibit the activity of the cyclin-cdk complexes 2 major categories: – INK4 family: p15Ink4b, p16Ink4a, p18Ink4c, p19Ink4d inhibit the activity of G1 cyclin cdks (e.g. cyc-D/cdk-4/6) – Cip/Kip family: p21Cip1, p27Kip1, p57Kip2 inhibit the activity of all other cyc- cdk complexes (late G1-M) (e.g. cyc-E/cdk-2/ and cyc-A/cdk-2) their expression is strongly stimulated by DNA damage => p53 activation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cyclin-dependent kinase inhibitors (CKIs) Cdk (catalytic subunit) Cyclin (regulatory subunit) DNA Inducer Cell cycle damage (e.g. p53) arrest CDK inhibitor (CKI) (inhibition) inhibition on CDK kinase activity p53: major tumour suppressor protein activated by DNA damage => causes cell cycle arrest at G1 phase Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Activation of p53 in Response to DNA Damage DNA Mutagen p53 destruction by proteasome DNA Damage Kinase 2 P activation DNA Repair p53 p53 e.g. Excision repair active inactive 1 Expression of CKIs: DNA Repair Cell cycle arrest Repair not possible: Apoptosis 3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The TP53 gene “The Guardian of the Genome” The TP53 gene encodes for p53 protein The p53 protein: o Detects DNA damage o Induces G1-G2 cell cycle arrest o Induces apoptosis Over 50% of cancers contain mutations in the TP53 gene Most commonly affected tumour suppressor gene in human cancer Levine and Oren. Nat Rev Cancer, 2009 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Internal and External Signals at the Checkpoints Both internal and external signals control the cell cycle progression at checkpoints Internal signals: e.g. cell size, incorrect alignment or separation of sister chromatids (at M phase checkpoint) External signals: e.g. environmental conditions, presence of growth factors Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  External signals Growth factors stimulate other cells to divide – Example: PDGF (platelet-derived growth factor) stimulates fibroblast growth in a wound or a culture Scalpels EXPERIMENT 1 A sample of connective tissue was cut up into small pieces. Petri Enzymes were used to digest the plate 2 extracellular matrix, resulting in a suspension of free fibroblast cells. 3 Cells were transferred to sterile culture vessels containing a basic growth medium consisting of glucose, amino acids, salts, Without PDGF and antibiotics (as a precaution against bacterial growth). PDGF was added to half the vessels. The culture vessels were With PDGF incubated at 37°C. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.17  External signals Density-dependent inhibition: crowded cells stop dividing Anchorage dependence: most animal cells must be attached to a substratum (support) in order to divide Normal Cells anchor to dish surface and mammalian cells: divide (anchorage dependence) The availability of When cells have formed a complete nutrients, growth single layer, they stop dividing factors, and a (density-dependent inhibition) substratum for attachment limits If some cells are scraped away, the cell remaining cells divide to fill the gap density to a single and then stop (density-dependent layer inhibition) 25 µm Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.18 A  Cancer cells: loss of cell cycle control Cancer cells do not exhibit density-dependent inhibition or anchorage dependence Cancer cells: Cancer Cancer cells do not exhibit cells usually anchorage dependence or continue to divide density-dependent inhibition well beyond a single layer, forming a clump of overlapping cells 25 µm Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.18 B The process by which a normal cell becomes a cancer cell is called transformation Normal cells Cancer cells Density dependent No Density dependent inhibition inhibition Anchorage dependence No anchorage dependence  Loss of Cell Cycle Controls in Cancer Cells Cancer cells do not respond normally to the body’s control mechanisms. Cancer cells: – make their own growth factors – have signaling pathways always ‘ON’ – Exhibit abnormal cell cycle control – form tumors: Benign tumors: not invasive, contained at a particular site Malignant tumors: invasive, can spread to other organs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Malignant tumours Malignant tumors invade surrounding tissues i.e. export cancer cells to other parts of the body where they may form secondary tumors (metastases) Tumor Lymph vessel Blood Glandular vessel tissue Cancer cell Metastatic Tumor 1 A tumour grows from 2 Cancer cells invade 3 Cancer cells spread 4 A small percentage of a single cancer cell neighbouring tissue through lymph and cancer cells may survive blood vessels to and establish a new tumour other parts of the body in another part of the body Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.19  Cancer cells’ characteristics Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Challenges to cancer treatment Cancer Cancerisiscaused causedbybyaccumulation accumulationofofmultiple multiplemutations mutations. Heterogeneity of tumours Diverse physiological pathways and tissue specificity Understanding of Cancer Landscape and Identification of Common Targets Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Challenges to cancer treatment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bert Vogelstein et al. Science 2013;339:1546-1558 Precision Oncology Precision Oncology: The science of using a patient’s genetics to create a treatment plan targeted to the molecular characteristics of their cancer Precision oncology is a rapidly developing area of research that is making its way, more and more, into mainstream oncology practice https://na.geneseeq.com/precision-oncology/#what-is-precision-oncology Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Summary: cell cycle checkpoints Cell cycle checkpoints: – G1 checkpoint: controls transition from G1 to S phase – G2 checkpoint: controls transition from G2 to M phase – M checkpoint: controls transition through the stages of Mitosis Cyclin-cdks (active form) can phosphorylate various proteins => cell cycle regulation Cell cycle regulation: https://www.youtube.com/watch?v=Jmqd9Qj_PTA https://www.youtube.com/watch?v=VLJF8Pf8spw Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Summary: Cell cycle control by cyc-cdks Cyclins Cdks G1 phase cyc-D and cyc-E cdk-2,4,6 S phase cyc-A cdk-2 G2/M phase cyc-A and cyc-B cdk-1 Note: cyc-A/cdk-1 and cyc-B/cdk-1 = MPF Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Summary of cell cycle regulation at Checkpoints G2/M transition: MPF activation (=> APC inactivation) – G1, S, G2 phases (interphase): APC active => MPF inactive – M phase: MPF active => APC inactive G1/S transition: Rb inactivation (phosphorylation)=> E2F release – Early G1 phase: Rb active => E2F inactive (bound to Rb) – Late G1, S, G2, M phases: Rb inactive => E2F active (released from Rb) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Summary of key steps of cell cycle regulation P Growth factors induce gene Rb E2F + RbP P E2F Active E2F expression Growth factor G1 cyclin-cdk complexes G1 checkpoint phosphorylate Rb p53 E2F is released, stimulating expression of genes required Control for S-phase system S DNA Cell replicates DNA (expression G1 replication of S-phase cyclin-cdk G2 complexes) M G2/M cyclin-cdk complexes cause cell to enter mitosis M checkpoint If DNA damage- p53 initiates Mitosis G2 checkpoint cell cycle arrest, DNA repair and if repair fails => apoptosis p53 (programmed cell death) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12.14  Healthy cells control their growth and will kill themselves if they become unhealthy... Activation of Apoptosis Tumour Mutation(s) Suppressor Genes Normal Cell containing Cell containing cell mutation(s) Activation of Cell mutation(s) Cycle Checkpoints and inhibition of Cell Cycle  Cancer cells cannot control their growth and cannot kill themselves... Cancer Cell Defective tumor Mutations containing suppressor genes Normal excessive cell mutations Uncontrolled cell division / Defective pathway of apoptosis Of course in real life things are more complicated… We described some of the key players involved…many more molecules/ mechanisms investigated/ under investigation Precision oncology is a rapidly developing area of research that is making its way, more and more, into mainstream oncology practice  SBA example 1 At which cell cycle phase is MPF active? A. G0 phase B. G1 phase C. S phase D. M phase E. Cytokinesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  SBA example 1 At which cell cycle phase is MPF active? A. G0 phase B. G1 phase C. S phase D. M phase E. Cytokinesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  SBA example 2 What does MPF consist of? A. Cyc-A/cdk-1 B. Cyc-A/cdk-2 C. Cyc-B/cdk-2 D. Cyc-D/cdk-1 E. Cyc-E/cdk-2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  SBA example 2 What does MPF consist of? A. Cyc-A/cdk-1 B. Cyc-A/cdk-2 C. Cyc-B/cdk-2 D. Cyc-D/cdk-1 E. Cyc-E/cdk-2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings